Finding the Fourth Proportional to 1,081.60, 1,491.52 and 639.52

Step by Step Solution

1. Step 1: Write the proportion equation
   1,081.60 : 1,491.52 = 639.52 : x
2. Step 2: Convert to fraction form
   1,081.60/1,491.52 = 639.52/x
3. Step 3: Cross multiply
   1,081.60x = 1,491.52 × 639.52
4. Step 4: Simplify right side
   1,081.60x = 953,856.87
5. Step 5: Solve for x
   x = 953,856.87/1,081.60
6. Step 6: Final answer
   x = 881.89